Temporal dynamics of electroconvulsive therapy induced seizures

Objective: Electroconvulsive therapy (ECT) is an effective treatment for several psychiatric disorders. The role of cortex and thalamus in seizure expression and termination seems critical. Here we study spatiotemporal dynamics of ECT-induced seizures based on electroencephalogram (EEG) features and biophysical parameters using a corticothalamic mean-field model. Methods: We analyzed 345 ictal EEGs from 33 patients (19 female). EEG features included the dominant frequency, and temporal and spatial correlations. A corticothalamic biophysical model assessed cortical excitation/inhibition (E/I) balance and effective corticothalamic and intrathalamic loop strengths. We tracked the temporal evolution of each feature and parameter from seizure onset to termination. Results: ECT-induced seizures showed EEG slowing (i.e., a decrease in dominant frequency) and increased temporal correlations as seizures approached termination. Cortical E/I ratios and corticothalamic loop strength increased, while intrathalamic strength decreased. Both EEG slowing and increase in temporal correlations were associated with increased cortical E/I ratios and decreased intrathalamic loop strength. Conclusions: ECT-induced seizures show slowing and increased temporal correlations toward termination. These dynamics may be driven by increased cortical E/I ratios and decreased intrathalamic loop strength. Significance: ECT-induced seizures exhibit characteristic temporal corticothalamic dynamics.